1. Field of the Invention
This invention relates, in general, to hydraulic couplings, and specifically to hydraulic couplings used in undersea drilling and production applications. More particularly, the invention involves a removable bore liner for an undersea hydraulic coupling member.
2. Description of Related Art
Subsea hydraulic couplings are old in the art. The couplings generally consist of a male member and a female member with seals to seal the junction between the male and female members. The female member generally has a cylindrical body with a relatively large diameter bore at one end and a relatively small diameter bore at the other. The small bore facilitates connections to hydraulic lines, while the large bore contains the seals and receives the male portion of the coupling. The male member includes a probe section insertable into the large bore of the female member. According to various embodiments of the device, the seals either abut the end, or face, of the male member or engage the male member about its outer circumference. Hydraulic fluid is then free to flow through the female and male portions of the coupling and seals prevent that flow from escaping about the joints of the coupling.
Optionally, a check valve may be installed in the female member and also in the male member. Each check valve is open when the coupling is made up; however, each check valve closes when the coupling is broken so as to prevent fluid from leaking out of the system of which the coupling is part.
In U.S. Pat. Nos. 4,694,859 and 5,762,106 to Robert E. Smith III, an undersea hydraulic coupling and metal seal is disclosed. A reusable metal seal engages the circumference of the probe when it is positioned within the female member body. The seal is held in place by a cylindrical seal retainer. When the male and female portions of the coupling are parted under pressure, the seal retainer prevents the metal seal from blowing out through the bore of the female member.
U.S. Pat. Nos. 4,900,071 and 5,052,439 to Robert E. Smith III disclose an undersea hydraulic coupling with an elastomeric seal that is restrained from radial movement into the central bore of the female member by a circumferential shoulder on one or both surfaces adjacent the seal. Preferably, the seal has a dovetail interfit with one or both surfaces. U.S. Pat. Nos. 5,099,882, 5,203,374, 5,232,021 to Robert E. Smith III also show undersea hydraulic couplings with these seals. An inner cylindrical surface of the annular seal engages the circumference of the male member or probe as the probe is inserted into the female member. As the male member or probe is pulled out of the female member bore, the leading face of the male member reaches the soft annular seal intermediate that bore. When the face reaches the midpoint of the soft annular seal, the dovetail interfit prevents the seal being imploded into the bore, as the seawater and/or hydraulic fluid enter the bore at high pressure.
To retain one or more seals in the female member of an undersea hydraulic coupling, a seal retainer may be attached to the female member. The seal retainer may be a generally sleeve-shaped cylindrical body that is inserted into the bore of the female member until the seal retainer abuts a shoulder in the bore of female member. To secure the seal retainer against the shoulder, a retainer locking member may also be attached to the female member using threads or snap rings, for example. A radial seal may be retained between the seal retainer and retainer locking member. Additionally, one or more face seals may be positioned between the seal retainer and shoulder.
In subsea drilling and production applications, female coupling members may be disengaged and re-engaged from male coupling members repeatedly. After disengagement, it is common that the male coupling members remain undersea and the female coupling members retrieved. Insertion of the male coupling member into the bore of the female coupling member, or removal of the male coupling member from the bore, may result in galling of the surfaces of the probe and/or bore. Galling may be caused, for example, by significant misalignment, or even very slight misalignment, of the male and female coupling members during their engagement or disengagement. In general, galling of the male and/or female coupling members is a serious problem because of damage to the sealing surfaces that are important to maintain fluid tight seals to block leakage of hydraulic fluid and/or entry of seawater into the coupling at high pressure. Additionally, after a sealing surface of either coupling member becomes galled, it may be more likely to gall again.
In the past, some male undersea hydraulic coupling members have been made from material with greater hardness, strength and yield than the material used to make female coupling members. The difference in hardness is intended to help reduce the galling problem. However, it is desirable to produce both the male and female coupling members from higher strength, higher yield materials, especially as hydraulic pressures and/or subsea pressures increase at greater depths where subsea hydraulic systems are located. Accordingly, an undersea hydraulic coupling is needed that will reduce or prevent the galling problem due to repeated engagement and disengagement of the coupling members.